KR20130072915A - Apparatus and method for roughing mill - Google Patents

Abstract

The present invention relates to a rough rolling apparatus and a method capable of preventing an accident caused by a speed difference between rough rolling rolls, and in particular, the rough rolling method according to an embodiment of the present invention includes first rolling before finishing rolling the cast steel. A rough rolling method in which the rolls to the fourth rolling roll are sequentially passed to roll in a bar state, wherein the rolled bars are sequentially passed through the first to third rolling rolls at the time of entry into the fourth rolling roll. Reducing the speed of the rolling roll; Monitoring the speed of the bar entering the fourth rolling roll; Determining whether the speed of the bar in the fourth rolling roll falls below a predetermined value; And controlling the bar speed in the third rolling roll when the speed of the bar in the fourth rolling roll has dropped below a set value.

Description

[0001] APPARATUS AND METHOD FOR ROUGHING MILL [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rough rolling apparatus and method, and more particularly, to a rough rolling apparatus and method capable of preventing an accident caused by a speed difference between rough rolling rolls.

The integrated steel mill produces various kinds of steel products from iron ore as raw material through a series of processes such as steel making -> steel making -> continuous casting -> hot rolling.

Briefly describing each process, steelmaking is a process of obtaining molten iron by charging hot air from the bottom after charging the ingot-shaped iron ore and coke through the upper part of the blast furnace. It is a process of obtaining molten steel by removing impurities through various stages of component adjustment such as refining.

Continuous casting is a process of continuously cooling and solidifying molten steel in a liquid state through a continuous casting machine in a curved shape to obtain an intermediate material such as a slab having various thicknesses and widths and rolling the intermediate material through rough rolling and finish rolling It is the final rolling process with the desired thickness and width.

In particular, the rolling is divided into a hot rolling process and a cold rolling process. In the hot rolling process, a slab heated to a proper temperature in a heating furnace process is rolled in a bar having a predetermined thickness in a rough rolling process and then sent to a final finishing mill. It refers to the final rolling process in the rolling process to the thickness ordered by the customer.

The general hot rolling process is specifically known in "continuous continuous hot rolling system and method (Patent No. 10-1067758).

FIG. 1 is a view showing a general rough rolling facility. The rough rolling facility is disposed between the heating furnace 3 and the coil box facility 4, and the casting 1 is placed in a bar 2 state A plurality of rolling rolls 10 are arranged apart from each other for rolling. For example, the rolling rolls 10 are each provided with a pair of upper and lower rolling rolls 11 and 12, in which four rolling rolls 10 are arranged sequentially, 10 will be referred to as a first rolling roll R1, a second rolling roll R2, a third rolling roll R3 and a fourth rolling roll R4 sequentially in accordance with the moving direction of the cast strip 1.

The cast steel 1 heated in the heating furnace is passed through the first rolling rolls R1 to R4 successively and the bars 2 having a constant thickness are produced by the pressure applied by the respective rolling rolls 10, A phenomenon such as a loop and a necking may occur between the rolling rolls 10 if the balance between the reduction rate at each rolling roll 10 and the speed of the casting 1 is not matched. Particularly, phenomena such as loops and necking occur between the first rolling rolls R1 and the second rolling rolls R2 having a relatively large interval and between the second rolling rolls R2 and R3. However, when the balance between the reduction rate and the speed of the cast strip 1 is not matched between the third and fourth rolling rolls R3 and R4 with relatively narrow intervals, The impact drop is so severe that loops or necking often occur.

However, in the conventional AMTC (Automatic Mill Tension Control) control, there is no control logic for the bar tip, and there is a problem that the bar and the neck are frequently scratched and nicked at the tip of the bar.

Patent No. 10-1067758 (September 20, 2011)

The present invention provides a rough rolling apparatus and a method for preventing accidents such as loops and necking caused by a difference in rough rolling speed between rough rolls for a steel product having high high temperature strength.

A rough rolling apparatus according to an embodiment of the present invention is an rough rolling apparatus for rolling a cast steel into a bar state before finish rolling, and includes a first rolling roll to a fourth rolling roll, A rolling roll; Speed measuring means for measuring a speed of a bar passing through the third rolling roll and the fourth rolling roll; And a control unit for controlling the bar speed or the reduction rate of the fourth rolling roll in the third and fourth rolling rolls according to the speed measured by the speed measuring means.

The control unit may reduce the speed of the third rolling roll when the speed of the bar decreases by 10% or more in the fourth rolling roll.

The rough rolling method according to one embodiment of the present invention is a rough rolling method for rolling a cast steel in a bar state sequentially through a first rolling roll to a fourth rolling roll prior to finish rolling, Lowering the speed of the fourth rolling roll at the time when the bar rolled while passing through the third rolling roll sequentially enters the fourth rolling roll; Monitoring the speed of the bar entering the fourth rolling roll; Determining whether the speed of the bar in the fourth rolling roll falls below a predetermined value; And controlling the bar speed in the third rolling roll when the speed of the bar in the fourth rolling roll has dropped below a set value.

And the speed of the fourth rolling roll is lowered within a range of 10% in the step of lowering the speed of the fourth rolling roll.

In the determining step, the set value is characterized in that the speed corresponding to 10% of the fourth rolling roll speed.

In the step of controlling the bar speed in the third rolling roll, the bar speed V3 in the third rolling roll is determined by the following formula (1).

[Equation 1]

V3 = V4 x T4 / T3

Here, V4 is the bar speed in the fourth rolling roll, T4 is the thickness of the fourth rolling roll out side bar, and T3 is the thickness of the third rolling roll out side bar.

And reducing the reduction rate of the fourth rolling roll by 0.5% when the speed of the bar in the fourth rolling roll falls below a set value.

The cast steel is a steel grade having a strength of 45 MPa or more at 950 ° C.

According to the embodiments of the present invention, when the bar passing through the roughing roll enters the fourth rolling roll and is rolled, the bar speed in the third rolling roll is appropriately controlled according to the speed of the bar in the fourth rolling roll, Occurrence of an accident such as a loop or necking occurring between the roll and the fourth rolling roll can be prevented.

Thereby, there is an effect that the scratches caused by the scratching of the tip portion of the bar on the mill side guide can be fundamentally suppressed.

1 is a view showing a general rough rolling facility,
2 is a schematic view showing a rough rolling apparatus according to an embodiment of the present invention,
3 is a flowchart showing a rough rolling method according to an embodiment of the present invention,
FIG. 4A is a graph showing the speed change of the third rolling roll and the fourth rolling roll according to the conventional rough rolling method,
4B is a graph showing a change in velocity of the third rolling roll and the fourth rolling roll according to the rough rolling method of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know. Wherein like reference numerals refer to like elements throughout.

FIG. 2 is a schematic view showing a rough rolling apparatus according to an embodiment of the present invention, and FIG. 3 is a flowchart showing a rough rolling method according to an embodiment of the present invention.

As shown in the drawings, the rough rolling apparatus according to an embodiment of the present invention includes: a first rolling roll R1 to a fourth rolling roll R4 that sequentially pass a cast steel and rough roll the steel into a bar 2 state; A speed measuring means (20) for measuring the speed of the bar (2) passing through the third rolling roll (R3) and the fourth rolling roll (R4); And a control unit (30) for controlling the speed of the bar (2) in the third rolling roll (R3) and the fourth rolling roll (R4) according to the speed measured by the speed measuring means (20).

The rolling roll 10 is a means for rolling a cast slab heated in a heating furnace in the form of a bar 2 having a desired thickness and is provided with a pair of upper and lower rolling rolls 11 and 12, Rolling rolls 10 are sequentially arranged. At this time, each of the rolling rolls 10 sequentially rolls the first rolling roll R1, the second rolling roll R2, the third rolling roll R3, the fourth rolling roll R4 ).

The distance between the first rolling roll R1 and the second rolling roll R2 is about 30 m and the distance between the second rolling roll R2 and the third rolling roll R3 is about 60 m, The distance between the third rolling roll R3 and the fourth rolling roll R4 is about 8 m. Since the interval between the third rolling roll R3 and the fourth rolling roll R4 is narrower than the interval between the other rolling rolls, the present invention is advantageous in that the speed balance between the third rolling roll R3 and the fourth rolling roll R4 .

Particularly, in the case of ordinary carbon steel, relatively high temperature physical properties are low and a speed drop of the third rolling roll R3 occurs due to the impact drop of the fourth rolling roll R4. The effect of the present invention on the quality of the product is negligible. On the other hand, in the case of the high-strength steel sheet, the speed drop of the third rolling roll R3 due to the impact drop of the fourth rolling roll R4 Speed Drop) occurs, a loop phenomenon occurs. It is preferable that the present invention is applied to a steel material having high high temperature strength. In this case, the steel having high strength at high temperature generally means a steel having a strength of 45 MPa or more at 950 DEG C, for example, stainless steel 304 steel is a typical high-strength steel. Of course, the rough rolling method according to the present invention is not limited to the one used for rough rolling a high-strength steel sheet, but may be applied to various rough rolling processes in which a phenomenon such as a loop or necking is caused by a phenomenon in which the speed balance between rolls is not matched It will be possible.

Meanwhile, in the present invention, a separate speed measuring means 20 for accurately measuring the speed of the bar 2 passing through the third rolling roll R3 and the fourth rolling roll R4 in real time is provided.

The speed measuring means 20 measures the speed of the bar 2 passing through the third rolling roll R3, the speed of the bar 2 entering the fourth rolling roll R4 and the speed of the fourth rolling roll R4 The speed of the passing bar 2 is precisely measured.

The speed measuring means 20 used at this time may be implemented with various means for measuring the progress speed of the bar 2.

The control unit 30 controls the speed of the third rolling roll R3 and the fourth rolling roll R4 or the reduction rate of the fourth rolling roll R4 according to the speed measured by the speed measuring unit 20 ).

In particular, the controller 30 lowers the speed of the third rolling roll (R3) when an impact drop in which the speed of the bar (2) is reduced by 10% or more in the fourth rolling roll (R4) occurs. The steps of controlling the speeds of the third rolling roll R3 and the fourth rolling roll R4 or the rolling reduction ratio of the fourth rolling roll R4 in the control unit 30 will be described in detail in the rough rolling method .

A rough rolling method in which a cast steel is rolled in the form of a bar using the above-described rough rolling apparatus will be described with reference to the drawings.

In the rough rolling method according to the present invention, when the high-strength high-strength steel having a strength of 45 MPa or more at 950 DEG C is roughly rolled, the main strips heated in the heating furnace are subjected to the first to third rolling rolls (R1 to R3) At the time when the bar 2 drawn out from the third rolling roll R 3 enters the fourth rolling roll R 4 and is manually rolled in the form of the bar 2 while passing through the fourth rolling roll R 4 ). ≪ / RTI > At this time, the speed of the fourth rolling roll (R4) is lowered within the range of 10%. Thus, the speed balance between the third rolling roll (R3) and the fourth rolling roll (R4) according to the high-temperature strength high-strength type is maintained. If the speed of the fourth rolling roll R4 is lowered by more than 10%, the speed balance with the third rolling roll R3 is not matched to the fourth rolling roll R4, and a loop phenomenon occurs Lt; / RTI >

Thus, rough rolling of the bar 2 by the 4th rolling roll R4 is performed continuously in the state which reduced the speed of the 4th rolling roll R4 in 10% or less of range. During the rough rolling of the bar 2 by the fourth rolling roll R4, the speed measuring means 20 is used to continuously monitor the speed of the bar that has entered the fourth rolling roll R4, 30).

The control unit 30 continuously monitors the speed of the bar 2 that has entered the fourth rolling roll R4 and determines whether the speed of the bar 2 in the fourth rolling roll R4 is lowered to a set value or more . The set value is preferably a speed corresponding to 10% of the fourth rolling roll (R4) speed. The reason for this is that as described above, when the phenomenon that the speed of the fourth rolling roll R4 decreases by 10% or more without the speed control of the third rolling roll R3 occurs, the bar enters the fourth rolling roll R4 (2). This is because a loop phenomenon occurs at).

If the speed of the bar 2 entering the fourth rolling roll R4 is continuously monitored by the control unit 30 and the speed of the bar 2 is lowered by 10% or more in the fourth rolling roll R4, and controls the bar speed in the third rolling roll R3 if an impact drop has occurred.

At this time, the bar speed V3 in the third rolling roll R3 is preferably determined by the following equation (1).

[Equation 1]

V3 = V4 x T4 / T3

Here, V4 is the bar speed in the fourth rolling roll R4, T4 is the thickness of the outgoing bar of the fourth rolling roll R4, and T3 is the thickness of the outgoing bar of the third rolling roll R3.

When an impact drop occurs in which the speed of the bar is lowered by 10% or more in the fourth rolling roll R4, the bar speed in the third rolling roll R3 is controlled, (0.5% lowering adjustment) so that the rolling reduction of the roll R4 is reduced from 9% to 8.5%. Thus, it is possible to prevent the occurrence of the loop phenomenon in the bar between the fourth rolling roll R4 and the third rolling roll R3 desirable.

When the rough rolling is carried out while the speed of the fourth rolling roll R4 and / or the third rolling roll R3 is lowered and the point 15m from the front end of the bar 2 passes all the fourth rolling roll R4 The speeds of the fourth rolling roll R4 and the third rolling roll R3 are restored to the original state and rough rolling is carried out in accordance with the conventional AMTC control (rough rolling setting value of a general steel).

Experiments were carried out to investigate the stability improvement of the operation according to the rough rolling method as described above.

FIG. 4A is a graph showing the speed change of the third rolling roll and the fourth rolling roll according to the conventional rough rolling method, and FIG. 4B is a graph showing changes in speed of the third rolling roll and the fourth rolling roll according to the rough rolling method of the present invention FIG.

First, as a comparative example, stainless steel 304, which is a high-strength stainless steel, is fed to a fourth rolling roll (R4) according to a conventional rough rolling method while maintaining 250 mpm without controlling the speed of the fourth rolling roll The rolling process was performed, and the change in speed of the third rolling roll R3 and the fourth rolling roll R4 was shown in FIG. 4A.

In the embodiment, the speed of the fourth rolling roll R4 is lowered from 250 to 230 mpm when the bar enters the fourth rolling roll R4 according to the rough rolling method of the present invention, And the velocity changes of the third and fourth rolling rolls (R 3 and R 4) are shown in FIG. 4 (b).

As shown in FIG. 4A, the comparative example produced about 15% of the impact drop in the fourth rolling roll R4, whereas in the fourth rolling roll R4, as shown in FIG. 4B, about 5% It was confirmed that only the impact drop of the impact was generated.

According to the experimental results, it was confirmed that the impact drop can be remarkably lowered according to the present invention. In order to reduce the strength at which the impact drop is generated, the third rolling rolls R3 and R4, So that it is possible to prevent accidents such as loops or necking that occur because the speed balance between the third rolling roll R3 and the fourth rolling roll R4 is not matched.

Although the present invention has been described with reference to the accompanying drawings and the preferred embodiments described above, the present invention is not limited thereto but is limited by the following claims. Accordingly, those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the spirit of the following claims.

1: slab 2: bar
10: rolling roll 20: velocity measuring means
30:
R1: first rolling roll R2: second rolling roll
R3: third rolling roll R4: fourth rolling roll

Claims (8)

A rough rolling apparatus for rolling a cast steel into a bar state before finish rolling,
A first rolling roll to a fourth rolling roll for sequentially passing the cast steel and rough rolling the steel into a bar state;
Speed measuring means for measuring a speed of a bar passing through the third rolling roll and the fourth rolling roll;
And a control unit for controlling a bar speed or a rolling reduction rate of the fourth rolling roll in the third and fourth rolling rolls according to the speed measured by the speed measuring means.
The method according to claim 1,
The control unit is a rough rolling apparatus, characterized in that for reducing the speed of the third rolling roll when the speed of the bar is reduced by 10% or more in the fourth rolling roll.
There is provided a rough rolling method in which a casting is sequentially rolled from a first rolling roll to a fourth rolling roll to effect rolling in a bar state,
Lowering the speed of the fourth rolling roll at the time when the rolled bar passes through the first rolling roll to the third rolling roll in succession and enters the fourth rolling roll;
Monitoring the speed of the bar entering the fourth rolling roll;
Determining whether the speed of the bar in the fourth rolling roll falls below a predetermined value;
And controlling the bar speed in the third rolling roll when the speed of the bar in the fourth rolling roll has dropped below a set value.
The method according to claim 3,
In the step of lowering the speed of the fourth rolling roll, the speed of the fourth rolling roll is reduced in the range of 10% or less rough rolling method.
The method according to claim 3,
In the determining step, the set value is a rough rolling method, characterized in that the speed corresponding to 10% of the fourth rolling roll speed.
The method according to claim 3,
Wherein in the step of controlling the bar speed in the third rolling roll, the bar speed (V3) in the third rolling roll is determined by the following formula (1).
[Equation 1]
V3 = V4 x T4 / T3
Here, V4 is the bar speed in the fourth rolling roll, T4 is the thickness of the fourth rolling roll out side bar, and T3 is the thickness of the third rolling roll out side bar.
The method according to claim 3,
Further comprising the step of lowering the reduction rate of the fourth rolling roll by 0.5% when the speed of the bar in the fourth rolling roll falls below a set value.
The method according to any one of claims 3 to 7,
Wherein the cast steel is a steel having a strength of at least 45 MPa at 950 ° C.

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